Real world data on effectiveness, safety and therapeutic drug monitoring of vedolizumab in patients with inflammatory bowel disease. A single center cohort

Background and aims: The efficacy of vedolizumab (VDZ) has been demonstrated in clinical trials. The aim of this report is to evaluate the long-term effectiveness and safety of VDZ in a real-world cohort and to explore possible associations between concentration measurements of VDZ and treatment effectiveness. Methods: This is a prospective clinical follow-up including all adult patients with ulcerative colitis (UC) and Crohn's disease (CD) treated with VDZ from October 2014 until September 2017 at a single center in Norway. The patients were followed for at least 14 weeks or until termination of treatment. Clinical and biochemical activity were obtained at every infusion throughout follow-up. Plasma measurements of VDZ (p-VDZ) were performed before every infusion during maintenance therapy. Results: In total, 71 patients received VDZ. Improvement of CRP and hemoglobin was observed in CD but not in UC, whereas Partial Mayo Score improved in UC while no change in Harvey Bradshaw Index was revealed in CD. Furthermore, CRP at baseline was negatively correlated with p-VDZ at week 14 in CD but not in UC patients. Conclusion: Improvement of biochemical markers of inflammation was observed in CD while clinical activity scores improved in UC patients. For CD, baseline CRP was correlated with lower concentrations of p-VDZ at week 14.